Graphite carbon nitride(g-C_(3)N_(4)) is a promising non-metal photocatalyst for photocatalytic hydrogen production, but its performance is still limited due to sluggish charges separation and low utilization of light...Graphite carbon nitride(g-C_(3)N_(4)) is a promising non-metal photocatalyst for photocatalytic hydrogen production, but its performance is still limited due to sluggish charges separation and low utilization of light.In this work, P-doped and N-doped carbon dots(NCDs) supported g-C_(3)N_(4)were successfully prepared via hydrothermal and polymerization reactions. The sub-bandgap formed by P-doping enhances the utilization of visible light, and the high electron density of P sites is conducive to the trapping of holes. NCDs also improve light utilization and, more importantly, act as electron acceptors and transporters to promote electron transport. The built-in electric field formed by the synergy of P-doping and NCDs-loading greatly promotes the separation of charges. The PCN/NCDs showed a significantly improved hydrogen evolution activity of 3731 μmol h^(-1)g^(-1), which was 6.7 times that of pure carbon nitride(560 μmol h^(-1)g^(-1)). This strategy may be generalized to the design of g-C_(3)N_(4)-based photocatalysts, facilitating the separation of charges for enhanced catalytic activity.展开更多
Al2O3-SiC composite was synthesized with pyrophyllite and natural graphite as raw materials by carbothermal reduction reaction under argon atmosphere. The effect of synthesis temperature on phase composition and micro...Al2O3-SiC composite was synthesized with pyrophyllite and natural graphite as raw materials by carbothermal reduction reaction under argon atmosphere. The effect of synthesis temperature on phase composition and microstructure was investigated. Low-carbon MgO-C refractories were prepared by using the synthesized Al2O3-SiC composite as additive. The effect of its addition on the slag penetration and corrosion resistance as well as oxidation resistance of the refractories was investigated, and the slag resistance and oxidation resistance mechanisms of the Al2O3-SiC composite were also discussed. The results show that the synthesis temperature has a great influence on preparation of Al2O3-SiC composite. The Al2O3-SiC composite can be synthesized at 1873-1973 K under argon atmosphere, with pyrophyllite and natural graphite as raw materials, and particle sizes of the composite synthesized at 1973 K are mainly distributed as 1-2 μm. The slag penetration and corrosion resistance of low-carbon M80-C refractories can be remarkably improved by adding the synthesized Al2O3-SiC composite, and the oxidation resistance has an improvement to some extent. The increase of slag viscosity and the formation of MgAl2O4 can effectively inhibit the slag penetration and corrosion for the refractories.展开更多
Due to the complex core-shell structure and variety of surface functional groups,the photoluminescence(PL)mechanism of carbon dots(CDs)remain unclear.o-Phenylenediamine(oPD),as one of the most common precursors for pr...Due to the complex core-shell structure and variety of surface functional groups,the photoluminescence(PL)mechanism of carbon dots(CDs)remain unclear.o-Phenylenediamine(oPD),as one of the most common precursors for preparing red emissive CDs,has been extensively studied.Interestingly,most of the red emission CDs based on oPD have similar PL emission characteristics.Herein,we prepared six different oPD-based CDs and found that they had almost the same PL emission and absorption spectra after purifiication.Structural and spectral characterization indicated that they had similar carbon core structures but diffferent surface polymer shells.Furthermore,single-molecule PL spectroscopy confirmed that the multi-modal emission of those CDs originated from the transitions of different vibrational energy levels of the same PL center in the carbon core.In addition,the phenomenon of"spectral splitting"of single-particle CDs was observed at low temperature,which confirmed these oPD-based CDs were unique materials with properties of both organic molecules and quantum dots.Finally,theoretical calculations revealed their potential polymerization mode and carbon core structure.Moreover,we proposed the PL mechanism of red-emitting CDs based on oPD precursors;that is,the carbon core regulates the PL emission,and the polymer shell regulates the PL intensity.Our work resolves the controversy on the PL mechanism of oPD-based red CDs.These findings provide a general guide for the mechanism exploration and structural analysis of other types of CDs.展开更多
The most widely used method of identification of microbial morphology and structure is microscopy,but it can be difficult to distinguish between pathogens with a similar appearance.Existing fluorescent staining method...The most widely used method of identification of microbial morphology and structure is microscopy,but it can be difficult to distinguish between pathogens with a similar appearance.Existing fluorescent staining methods require a combination of a variety of fluorescent materials to meet this demand.In this study,unique concentration-dependent fluorescent carbon dots(CDs)were synthesized for the identification and quantification of pathogens.The emission wavelength of the CDs could be tuned spanning the full visible region by virtue of aggregation-induced narrowing of bandgaps.This tunable emission wavelength of the specific concentration response to diverse microbes can be used to distinguish microorganisms with a similar appearance,even in a same genus.A hyperspectral microscopy system was demonstrated to distinguish Aspergillus flavus and A.fumigatus based on the results above.The identification accuracy of the two similar-looking pathogens can be close to 100%,and the relative proportions and spatial distributions can also be profiled from the mixture of the pathogens.This technique can provide a solution to the fast detection of microorganisms and is potentially applicable to a wide range of problems in areas such as healthcare,food preparation,biotechnology,and health emergency.展开更多
Currently,there is a strong drive to discover alternative materials that exhibit room-temperature phosphorescence(RTP)for displays,bioimaging,and data security.Ideally,these materials should be nontoxic,cheap,and poss...Currently,there is a strong drive to discover alternative materials that exhibit room-temperature phosphorescence(RTP)for displays,bioimaging,and data security.Ideally,these materials should be nontoxic,cheap,and possess controllable photoluminescent properties.Carbon dots(CDs)possess each of these characteristics,but to date,less attention has been paid to their RTP mechanism.Herein,we synthesized a series of CDs by self-crosslinking and carbonization of precursor.The resultant CDs were luminescent and exhibited a bright,micro-second afterglow lifetime.To increase the RTP,a second microwave processing step was used to coat the CDs with polyvinyl alcohol(PVA),polyacrylamide(PAM),or tetraethyl orthosilicate(TEOS),producing CDs@PVA,CDs@PAM,and CDs@TEOS composites.The core-shell structure acted to enhance crosslinking at the surface of the CDs to boost the RTP,creating abundant energy levels for intersystem crossover.In situ X-ray photoelectron spectroscopy verified electron transfer during luminescence.Finally,we present a design rule that can be used to tune the quantum yields and RTP lifetime of CDs,based on the effective stabilization of triplet excited states through the extent and strength of cross-linking.This simple strategy provides a flexible route for guiding the further development of CDs with tailored RTP properties for various applications.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 52122308, 21905253,51973200, U21A20329)the Natural Science Foundation of Henan(No. 202300410372)+1 种基金the Key Scientific Research Projects of Higher Education Institutions in Henan ProvinceChina (No.21A150054)。
文摘Graphite carbon nitride(g-C_(3)N_(4)) is a promising non-metal photocatalyst for photocatalytic hydrogen production, but its performance is still limited due to sluggish charges separation and low utilization of light.In this work, P-doped and N-doped carbon dots(NCDs) supported g-C_(3)N_(4)were successfully prepared via hydrothermal and polymerization reactions. The sub-bandgap formed by P-doping enhances the utilization of visible light, and the high electron density of P sites is conducive to the trapping of holes. NCDs also improve light utilization and, more importantly, act as electron acceptors and transporters to promote electron transport. The built-in electric field formed by the synergy of P-doping and NCDs-loading greatly promotes the separation of charges. The PCN/NCDs showed a significantly improved hydrogen evolution activity of 3731 μmol h^(-1)g^(-1), which was 6.7 times that of pure carbon nitride(560 μmol h^(-1)g^(-1)). This strategy may be generalized to the design of g-C_(3)N_(4)-based photocatalysts, facilitating the separation of charges for enhanced catalytic activity.
基金supported by the National Science and Technology Major Special Project (No.2009ZX04006-032)the National Natural Science Foundation of China (No.50274021) and Baoshan Iron and SteelCo.,Ltd.,China
文摘Al2O3-SiC composite was synthesized with pyrophyllite and natural graphite as raw materials by carbothermal reduction reaction under argon atmosphere. The effect of synthesis temperature on phase composition and microstructure was investigated. Low-carbon MgO-C refractories were prepared by using the synthesized Al2O3-SiC composite as additive. The effect of its addition on the slag penetration and corrosion resistance as well as oxidation resistance of the refractories was investigated, and the slag resistance and oxidation resistance mechanisms of the Al2O3-SiC composite were also discussed. The results show that the synthesis temperature has a great influence on preparation of Al2O3-SiC composite. The Al2O3-SiC composite can be synthesized at 1873-1973 K under argon atmosphere, with pyrophyllite and natural graphite as raw materials, and particle sizes of the composite synthesized at 1973 K are mainly distributed as 1-2 μm. The slag penetration and corrosion resistance of low-carbon M80-C refractories can be remarkably improved by adding the synthesized Al2O3-SiC composite, and the oxidation resistance has an improvement to some extent. The increase of slag viscosity and the formation of MgAl2O4 can effectively inhibit the slag penetration and corrosion for the refractories.
基金supported by the National Natural Science Foundation of China(52122308,21905253,51973200,and 52103239)Natural Science Foundation of Henan Province(202300410372)Henan Postdoctoral Foundation。
基金supported by the National Natural Science Foundation of China(52122308,21905253,51973200,22073046)the Natural Science Foundation of Henan(202300410372).
文摘Due to the complex core-shell structure and variety of surface functional groups,the photoluminescence(PL)mechanism of carbon dots(CDs)remain unclear.o-Phenylenediamine(oPD),as one of the most common precursors for preparing red emissive CDs,has been extensively studied.Interestingly,most of the red emission CDs based on oPD have similar PL emission characteristics.Herein,we prepared six different oPD-based CDs and found that they had almost the same PL emission and absorption spectra after purifiication.Structural and spectral characterization indicated that they had similar carbon core structures but diffferent surface polymer shells.Furthermore,single-molecule PL spectroscopy confirmed that the multi-modal emission of those CDs originated from the transitions of different vibrational energy levels of the same PL center in the carbon core.In addition,the phenomenon of"spectral splitting"of single-particle CDs was observed at low temperature,which confirmed these oPD-based CDs were unique materials with properties of both organic molecules and quantum dots.Finally,theoretical calculations revealed their potential polymerization mode and carbon core structure.Moreover,we proposed the PL mechanism of red-emitting CDs based on oPD precursors;that is,the carbon core regulates the PL emission,and the polymer shell regulates the PL intensity.Our work resolves the controversy on the PL mechanism of oPD-based red CDs.These findings provide a general guide for the mechanism exploration and structural analysis of other types of CDs.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61935010,61975069,21905253,and 51973200)the China Postdoctoral Science Foundation(Nos.2018M640681 and 2019T120632)+5 种基金the Natural Science Foundation of Henan(No.202300410372)Key-Area Research and Development Program of Guangdong Province(No.2020B090922006)Guangdong Project of Science and Technology Grants(No.2018B030323017)Guangzhou science and technology project(Nos.201903010042 and 201904010294)Youth project of science and technology research program of Chongqing Education Commission of China(No.KJQN202001322)the Science and Technology Development Fund from Macao SAR(File Nos.0125/2018/A3 and 0071/2019/AMJ).
文摘The most widely used method of identification of microbial morphology and structure is microscopy,but it can be difficult to distinguish between pathogens with a similar appearance.Existing fluorescent staining methods require a combination of a variety of fluorescent materials to meet this demand.In this study,unique concentration-dependent fluorescent carbon dots(CDs)were synthesized for the identification and quantification of pathogens.The emission wavelength of the CDs could be tuned spanning the full visible region by virtue of aggregation-induced narrowing of bandgaps.This tunable emission wavelength of the specific concentration response to diverse microbes can be used to distinguish microorganisms with a similar appearance,even in a same genus.A hyperspectral microscopy system was demonstrated to distinguish Aspergillus flavus and A.fumigatus based on the results above.The identification accuracy of the two similar-looking pathogens can be close to 100%,and the relative proportions and spatial distributions can also be profiled from the mixture of the pathogens.This technique can provide a solution to the fast detection of microorganisms and is potentially applicable to a wide range of problems in areas such as healthcare,food preparation,biotechnology,and health emergency.
基金supported by the National Natural Science Foundation of China(Nos.52122308,21905253,and 51973200)the Natural Science Foundation of Henan Province(No.202300410372).
文摘Currently,there is a strong drive to discover alternative materials that exhibit room-temperature phosphorescence(RTP)for displays,bioimaging,and data security.Ideally,these materials should be nontoxic,cheap,and possess controllable photoluminescent properties.Carbon dots(CDs)possess each of these characteristics,but to date,less attention has been paid to their RTP mechanism.Herein,we synthesized a series of CDs by self-crosslinking and carbonization of precursor.The resultant CDs were luminescent and exhibited a bright,micro-second afterglow lifetime.To increase the RTP,a second microwave processing step was used to coat the CDs with polyvinyl alcohol(PVA),polyacrylamide(PAM),or tetraethyl orthosilicate(TEOS),producing CDs@PVA,CDs@PAM,and CDs@TEOS composites.The core-shell structure acted to enhance crosslinking at the surface of the CDs to boost the RTP,creating abundant energy levels for intersystem crossover.In situ X-ray photoelectron spectroscopy verified electron transfer during luminescence.Finally,we present a design rule that can be used to tune the quantum yields and RTP lifetime of CDs,based on the effective stabilization of triplet excited states through the extent and strength of cross-linking.This simple strategy provides a flexible route for guiding the further development of CDs with tailored RTP properties for various applications.